Identifying linear models from time domain simulations

1997 ◽  
Vol 10 (2) ◽  
pp. 26-30 ◽  
Author(s):  
J.J. Sanchez-Gasca ◽  
K. Clark ◽  
N.W. Miller ◽  
H. Okamoto ◽  
A. Kurita ◽  
...  
Keyword(s):  
Time Domain ◽  
Linear Models

A Conjecture on the Interface Mechanics in Fractures Based on the Interpretation of Impulse Vests

1989 ◽  
Vol 203 (4) ◽  
pp. 203-205 ◽  
Author(s):  
J A Brandon ◽  
J Richards
Keyword(s):  
Fracture Healing ◽  
Linear Model ◽  
Time Domain ◽  
Linear Models ◽  
Callus Formation ◽  
Stiffness Model ◽  
Interface Mechanics ◽  
Static Mechanical ◽  
Characteristic Signal ◽  
Two Stages

Time-domain tests for monitoring fracture healing, undertaken by the authors and workers elsewhere, show a repeatable characteristic signal behaviour which is difficult to explain using the linear models prevailing in biomechanics. The paper proposes a simple non-linear model which, it is believed, will reproduce the observed signal behaviour and is consistent with the biphasic stiffness model previously identifed in static mechanical testing for monitoring of fracture healing. This, in turn, correlates with the two stages of callus formation in the accepted biological model.

Obtaining multi-loop pursuit-control pilot models from computer simulation

2008 ◽  
Vol 222 (2) ◽  
pp. 189-199 ◽  
Author(s):  
R A Hess
Keyword(s):  
Computer Simulation ◽  
Time Domain ◽  
Flight Control ◽  
Linear Models ◽  
Degree Of Freedom ◽  
Pilot Model ◽  
Pursuit Control ◽  
The Time Domain ◽  
Frequency Domain Techniques ◽  
Six Degree Of Freedom

A method for generating simplified pursuit-control pilot models for computer simulation of multi-axis flight control tasks has been developed. The method involves a sequential loop closure synthesis procedure for creating the pilot model and includes handling qualities estimation. The original model formulation previously reported in the literature used frequency-domain techniques, primarily Bode diagrams to select model gains. The present research demonstrates how similar results can be obtained in the time-domain. This latter approach is particularly useful when complex, non-linear aircraft models are being used. The time-domain approach is exercised in a six-degree of freedom rotorcraft control simulation and in a six-degree of freedom tailless fighter simulation, both involving linear models.

scholarly journals CONDUTIVIDADE ELÉTRICA DA SOLUÇÃO DE SOLO EM FUNÇÃO DA CONDUTIVIDADE ELÉTRICA APARENTE E DA UMIDADE DO SOLO SOB APLICAÇÃO DE CLORETO DE POTÁSSIO COM USO DA REFLECTOMETRIA NO DOMINIO DO TEMPO

Irriga ◽  
2005 ◽  
Vol 10 (2) ◽  
pp. 174-183
Author(s):  
Tibério Santos Martins da Silva ◽  
Vital Pedro da Silva Paz ◽  
Eugênio Ferreira Coelho ◽  
Maurício Antônio Coelho Filho ◽  
Gessionei Da Silva Santana
Keyword(s):  
Electrical Conductivity ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Soil Solution ◽  
Time Domain ◽  
Linear Models ◽  
Time Domain Reflectometry ◽  
Soil Electrical Conductivity ◽  
Bulk Electrical Conductivity

CONDUTIVIDADE ELÉTRICA DA SOLUÇÃO DE SOLO EM FUNÇÃO DA CONDUTIVIDADE ELÉTRICA APARENTE E DA UMIDADE DO SOLO SOB APLICAÇÃO DE CLORETO DE POTÁSSIO COM USO DA REFLECTOMETRIA NO DOMINIO DO TEMPO  Tibério Santos Martins da Silva1; Vital Pedro da Silva Paz2; Eugênio Ferreira Coelho3; Maurício Antônio Coelho Filho3; Gessionei da Silva Santana41Universidade Federal da Bahia,  Cruz das Almas, BA, tibé[email protected] de Engenharia Agrícola, Universidade Federal da Bahia, Cruz das Almas-BA, 3Embrapa Mandioca e Fruticultura, Cruz das Almas-BA4Universidade Federal de Viçosa, Viçosa, MG,   1 RESUMO O trabalho teve como objetivo definir, em campo e em laboratório, modelos matemáticos que melhor relacionam a condutividade elétrica aparente (CEa), a umidade do solo (q) e a condutividade elétrica da solução do solo (CEw) sob aplicação de cloreto de potássio, via água de irrigação por gotejamento. O experimento consistiu de leituras de CEa e q com um analisador de umidade de reflectometria no domínio do tempo (TDR) em colunas de solo em laboratório e em várias posições de uma malha retangular de um perfil do solo, em condições de campo, seguido da extração de solução iônica nas respectivas posições. Foram ajustados modelos lineares e não lineares relacionando CEa, q e CEw. O resultados permitiram concluir que a CEw da solução do solo pode ser monitorada a partir de leituras de CEa pela TDR para fins de distribuição de solutos no solo sob fertirrigação, com uso dos modelos de Rhoades et al. (1976), Vogeler et al. (1996), Nadler et al. (1984) e empírico em condições de campo e laboratório. O modelo de Rhoades et al. (1989) e Rhoades et al. (1976) mostraram-se adequados apenas para os estudos em laboratório. UNITERMOS: fertirrigação, TDR  SILVA, T. S. M. DA; PAZ, V. P. DA S.; COELHO, E. F.; COELHO FILHO, M. A.; SANTANA, G. DA S. SOIL SOLUTION ELECTRICAL CONDUCTIVITY AS A FUNCTION OF BULK ELECTRICAL CONDUCTIVITY AND SOIL WATER CONTENT UNDER POTASSIUM CLORIDE APPLICATION USING TIME DOMAIN REFLECTOMETRY  2 ABSTRACT This study aimed to define mathematical models that suitably relate bulk electrical conductivity (CEa), soil water content (q) and soil solution electrical conductivity (CEw) under potassium chloride application by drip irrigation. The experiment consisted of readings of CEa and q using a Time Domain Reflectometry analyzer (TDR) in soil columns in laboratory and on several positions of rectangular soil profile grid under field conditions. Ionic solution was extracted in all positions of TDR readings. Linear and non-linear models relating CEa, q and CEw were adjusted to laboratory and field data. Results allowed to conclude that CEw may be monitored by readings of CEa from TDR for soil solute distribution under fertirrigation, using models of Rhoades et al. (1976), Vogeler et al. (1996), Nadler et al. (1984) and an empirical model in lab and in field. The models of de Rhoades et al. (1989) e Rhoades et al. (1976) were suitable only for laboratory studies. KEYWORDS: fertirrigation, soil electrical conductivity, TDR

Auto-Tuning of Low-Order Controllers by Direct Manipulation of Closed-Loop Time Domain Measures

1996 ◽  
Vol 210 (1) ◽  
pp. 13-30
Author(s):  
A J Lawrence ◽  
C J Harris
Keyword(s):  
Time Domain ◽  
Process Model ◽  
Closed Loop ◽  
Linear Models ◽  
Process Models ◽  
System Response ◽  
Controller Tuning ◽  
Single Input Single Output ◽  
Real Process ◽  
Low Order

Many controller tuners are based on linear models of both the controller and process. Desired performance is often predetermined or adjusted in a manner that is not directly related to the desired response. All physical processes contain non-linearities, commonly of the actuator saturating type, and many controllers contain heuristics for implementation in real systems, such as anti-integral wind-up in PID (proportional integral differential) controllers. For different processes a range of closed-loop response shapes are desired, often described by features of the response such as rise time, overshoot and settling time. This paper investigates the possibility of basing controller tuning on closed-loop system response data such that desired performance is incorporated directly in terms of familiar time domain features or labels, thus eliminating the need for a mathematical process model and repeated tuning reformulations to achieve the desired performance. A controller tuning method named label-based neuro-tuning (LBNT) is developed and analysed by application to PID controller tuning for process models indicative of real process behaviour. Simulations and numerical investigation indicate that LBNT is a viable technique for the tuning of low-order SISO (single-input-single- output) controllers. Tuning is straightforward, flexible and copes well with process parametric changes and performance specification reformulation. The drawbacks are a complicated pretune phase, a limited selection of suitable labels and a difficulty in defining general classes of tuning problems for its application. The technique is not based on the assumption of process linearity, but due to the inability to characterize classes of input signals and operating points the types of process non-linearity are restricted. The controller may be non-linear, but must be structurally predetermined, and an input/output process model of arbitrary structure is required.

A Note on Effects of Digital Approximation in Linear Models

1974 ◽  
Vol 3 (9) ◽  
pp. 893-897
Author(s):  
Gerald McWilliams ◽  
James Poirot†
Keyword(s):  
Linear Models
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